Chemical Oxygen Demand Method Research Articles

Chemiluminescence method with potassium permanganate for the determination of organic pollutants in seawater.

A chemiluminescence method with potassium permanganate was developed for use as an indicator of organic pollutants in fresh water. This method could be applied to the determination of organic pollutants in seawater as well. However, the flow chemiluminescence method suffered from the interference of chloride ions at the same concentration of seawater because of the production of manganese dioxide in the oxidation of chloride ions with permanganate. The conditions (concentrations of potassium permanganate and sulfuric acid and sample volume, i.e. flow injection method) were chosen to minimize the interference of chloride ions. The chemiluminescence method shows a good correlation with the chemical oxygen demand method on fresh water added artificial sea salt and seawater samples. Natural seawater was analyzed by the chemiluminescence method. The results obtained were compared with those obtained by chemical oxygen demand under the alkaline condition and total organic carbon methods. The chemiluminescence method has higher sensitivity and reproducibility than the conventional chemical oxygen demand and total organic carbon methods.

Chemical oxygen demand determination in environmental waters by mixed-acid digestion and single sweep polarography

A new variant of the method for chemical oxygen demand (COD; 20–1100 mg O 2 l −1) determination in environmental waters is described. The method is based on determination of excess Cr(VI) in a mixed-acid (H 3PO 4–H 2SO 4) digestion solution by single sweep polarography instead of titrimetry; COD is measured indirectly. The reflux time is shortened to 15 min by mixed-acid digestion. The effects of mixed-acid concentration, reflux time, amounts of dichromate, supporting electrolyte, and interfering substances on COD determination are discussed. Preliminary application are made to waste waters and sewage. The results obtained are in good agreement with those given by the standard reflux method with a relative error<1.5%.

Ceriometry, a combined method for chemical oxygen demand and dissolved oxygen (with a discussion on the precision of the winkler technique)

A ceriometric method is described in which Ce3+ salts are used for the determination of dissolved oxygen and Ce4+ salts for the determination of the chemical oxygen demand. The interference of COD in the O2 determination, a common feature of most Winkler determinations, is corrected. The standard deviation is typically about 1% of the mean, and bias (inaccuracy) is very small.

Semi-Micro tube method for chemical oxygen demand

Semi-Micro tube method for chemical oxygen demand